Commonly assigned, U.S. Pat. Nos. 5,388,594, 5,505,214, and 5,591,368 disclose various electrically powered smoking systems comprising electric lighters and cigarettes. The systems provide smoking pleasure while significantly reducing sidestream smoke and permitting the smoker to selectively suspend and reinitiate smoking.
The preferred embodiment of the lighter in U.S. Pat. No. 5,388,594 includes a plurality of metallic serpentine heaters disposed in a configuration that slidingly receives a tobacco rod portion of the system's cigarette. The cigarette and the lighter are configured such that when the cigarette is inserted into the lighter and as individual heaters are activated for each puff, localized charring occurs at spots about the cigarette in the locality where each heater bears against the cigarette (hereinafter referred to as a "heater footprint").
In U.S. Pat. No. 5,388,594, the sequence and the amount of energy applied to each heater element during a puff cycle is regulated by a logic circuit of a controller which executes a power subroutine upon its receiving a signal from a puff sensor. The power subroutine includes the steps of reading the voltage of the power source (batteries) at the initiation of the puff and resolving a shut-off signal in cooperation with a constant Joules energy timer such that the duration of the pulse (its cycle-period) is adjusted relative to the voltage of the power source to provide the same total amount of energy (Joules) throughout the range of voltages of the battery discharge cycle.
Commonly assigned U.S. Pat. Nos. 5,388,594, 5,505,214, and 5,591,368 disclose cigarette designs including a tubular, tobacco-coated web that releases tobacco smoke constituents when heat is applied to the web. Preferably, the tobacco is coated along the interior of the web, and the web includes an unfilled portion or cavity so as to promote a more complete development of tobacco aerosol. The various forms of cavities (also called gaps and voids) improve delivery in electrically heated cigarettes.
U.S. Pat. No. 5,591,368 describes an electrical smoking system comprising an electric lighter having a plurality of electrically resistive heaters and a controller, together with a cigarette having a tubular tobacco web which is only partially-filled with cut tobacco shreds so as to define a filled tobacco rod portion and an unfilled tobacco rod portion. Preferably upon full insertion of the cigarette into the lighter, operative portions of heater elements within the lighter partially overlap both the aforementioned filled portion and the unfilled portion of the cigarette rod. With such overlap, an immediate release of tobacco smoke arises from the more readily combusted, unfilled tobacco rod portion so that the smoker receives an immediate response upon initiating a draw. Combustion of the filled tobacco rod portion is slightly delayed and contributes the aromas and taste of the tobacco or blend of tobaccos comprising the filled portion of the tobacco rod. Accordingly, the arrangement provides a smoker aspects of smoking pleasure to which he/she expects from smoking more traditional cigarettes; an immediacy of response and the tastes and aromas of filler tobaccos.
With the system of U.S. Pat. No. 5,591,368, it is important that the internal structures of the cigarette and lighter are match so that the desired proportions of heater overlap are achieved. Accordingly, a need has arisen for providing the lighter a capacity to discern whether a given cigarette that has been inserted in the lighter has the desired internal structure, particularly as to whether the cigarette includes a cavity within a tubular tobacco web. Further to this need, it is important that the cigarette and lighter of an electrical smoking system be matched so that the desired tastes and predetermined delivery levels are obtained.
The above-commonly assigned U.S. Pat. Nos. 5,388,594, 5,505,214, and 5,591,368 all disclosed systems which include a cigarette detector signal a logic circuit responsively to an insertion of a cigarette, some of which detectors include optical components. It has been found that lens and other light transmissive components located at or about the heater elements of the lighter are prone to collect dirt and/or tobacco smoke condensates and become clouded.
It has also been found that optical detectors may generate spurious signals if they are exposed to ambient (external) sources of light. This problem becomes aggravated as one attempts to locate such detectors away from the heater elements and closer to the entrance of the cigarette receiving port of the lighter.